Three-phase permanent magnet cascade claw type stepping motor

Abstract

A magnet type stepping motor which has (1) a stator with three-phase stator windings, and 6m pieces of stator main pole arranged side by side, where m is an integer and ≧1, the stator windings of one phase are wound around every two stator main poles among the 6m pieces of the stator main pole, wherein when the stator windings of one phase are excited with a direct current, m pieces of N pole and M pieces of S pole are formed alternately on the 6m pieces of stator main pole, and (2) a rotor of a cylindrical permanent magnet magnetized in the circumferential direction to form Z/2 pieces of N pole and Z/2 pieces of S pole alternately, where Z is the number of rotor poles.

What is claimed is: 
     
       1. A driving method of a three-phase annular winding cascade claw-pole type stepping motor comprising (1) a rotor consisting of a cylindrical magnet magnetized in the circumferential direction so as to form M pieces of N pole and M pieces S pole alternately, where M is an integer and ≧2, and (2) a stator having annular three stator units arranged in the axial direction of the rotor concentrically with the rotor axis, each of said stator unit consisting of two opposite stator cores having claw poles extending axially on the inner peripheral surface thereof, and of one of three stator windings of U, V and W phases held between said two stator cores, said windings of U, V and W phases being arranged in this order in the axial direction, said claw poles being separated by 180°/M from one another and magnetized by said stator winding in opposite polarities alternately, said three stator windings being connected to form a star or delta connection, adjacent claw poles magnetized by the stator windings of U phase and V phase are deviated by 60°/M from each other in the circumferential direction, and adjacent claw poles magnetized by the stator windings of V phase and W phase are deviated by 60°/M from each other in the circumferential direction, said annular stator windings being excited so that a magnetic flux generated by the annular stator windings of one phase in the axial direction becomes always opposite to that by annular stator windings of the other phase, in case of two phase exciting driving. 
     
     
       2. A driving method of a three-phase annular winding cascade claw-pole type stepping motor comprising a rotor consisting of a cylindrical magnet magnetized in the circumferential direction so as to form M pieces of N pole and M pieces S pole alternately, where M is an integer and ≧2, and   a stator having annular three stator units arranged in the axial direction of the rotor concentrically with the rotor axis each of said stator unit consisting of two opposite stator cores having claw poles extending axially on the inner peripheral surface thereof, and of one of three stator windings of U, V and W phases held between said two stator cores, said windings of U, V and W phases being arranged in this order in the axial direction, said claw poles being separated by 180°/M from one another and magnetized by said stator winding in opposite polarities alternately, said three stator windings being connected to form the star or delta connection, adjacent claw poles magnetized by the stator windings of U phase and V phase are deviated by 120°/M from each other in the circumferential direction, and adjacent claw poles magnetized by the stator windings of V phase and W phase are deviated by 120°/M from each other in the circumferential direction, wherein the magnetic flux generated by annular stator windings of one phase in the axial direction becomes always the same to that generated by the other annular stator windings of the other phase adjacent to said annular stator windings of said one phase, but a magnetic flux generated by the annular stator windings of one phase in the axial direction becomes always opposite to that generated by the annular stator windings of the other phase which is not adjacent to said annular stator windings of said one phase, in case of two phase exciting driving.   
     
     
       3. A driving method of a three-phase annular winding cascade claw-pole type stepping motor comprising a rotor consisting of a cylindrical magnet magnetized in the circumferential direction so as to form M pieces of N pole and M pieces S pole alternately, where M is an integer and ≧2, and a stator having annular three stator units arranged in the axial direction of the rotor concentrically with the rotor axis each of said stator unit consisting of two opposite stator cores having claw poles extending axially on the inner peripheral surface thereof, and of one of three stator windings of U, V and W phases held between said two stator cores, said windings of U, V and W phases being arranged in this order in the axial direction, said claw poles being separated by 180°/M from one another and magnetized by said stator winding in opposite polarities alternately, said three stator windings being connected to form the star or delta connection, adjacent claw poles magnetized by the stator windings of U phase and V phase are deviated by 120°/M from each other in the circumferential direction, and adjacent claw poles magnetized by the stator windings of V phase and W phase are deviated by 120°/M from each other in the circumferential direction, each of said annular stator windings having a center tap, said annular stator windings being excited by a unipolar circuit having six transistors so that a magnetic flux generated by the excited annular stator windings of one phase in the axial direction becomes always opposite to that generated by the excited annular stator windings of other phase, in case of two phase exciting driving.